Ah to Wh Converter
Convert amp-hours to watt-hours — or back — for any battery voltage. The honest way to compare battery capacity.
Energy
0 Wh
Wh = Ah × V
Rated capacity — usable energy depends on chemistry: ~50% for lead-acid, 80–100% for lithium.
Ah vs Wh — what's the difference?
Amp-hours (Ah) measure electric charge — how many amps a battery can supply for how long. Watt-hours (Wh) measure energy — charge × voltage. Since batteries come in different voltages, only Wh lets you compare them fairly: Wh = Ah × V.
| Battery | Ah | Voltage | Energy |
|---|---|---|---|
| Phone battery | 4.5 Ah (4,500 mAh) | 3.85 V | ≈ 17 Wh |
| Power bank (20,000 mAh) | 20 Ah | 3.7 V | 74 Wh |
| Car starter battery | 60 Ah | 12 V | 720 Wh |
| Leisure / RV battery | 100 Ah | 12 V | 1,200 Wh |
| Solar LiFePO4 rack unit | 100 Ah | 51.2 V | 5,120 Wh |
| EV battery (small) | ≈ 115 Ah | 350 V | ≈ 40,000 Wh |
Ah to Wh FAQ
How do I convert Ah to Wh?
Wh = Ah × battery voltage. A 100 Ah 12 V battery holds 1,200 Wh (1.2 kWh). Reverse: Ah = Wh ÷ V.
How many Wh is a 100Ah 12V battery?
1,200 Wh — but usable energy is less: ~600 Wh for lead-acid (50% depth of discharge), 960–1,200 Wh for LiFePO4.
Why do airlines limit batteries by Wh?
mAh doesn't state energy. A 20,000 mAh power bank at 3.7 V is 74 Wh — under the usual 100 Wh carry-on limit (100–160 Wh usually needs airline approval).
Can I compare batteries by Ah?
Only at the same voltage. 100 Ah at 24 V stores twice the energy of 100 Ah at 12 V — compare in Wh instead.